Singleton class concept in OO abap

Some times we have requirement that class can be instantiated only once or if i rephrase it , it will be we don't want that anybody else can create the object of the class if i have already created one and how can we achieve this functionality?? Please check below :

• First goto SE24 and create a class with instantiation as PRIVATE.
• Now create a constructor visibility as PRIVATE so that nobody can create instantiate the class.
• Now create a STATIC and public method GET_INSTANCE and write the below code .

           IF gref_obj is INITIAL.

                    CREATE OBJECT gref_obj.
           ENDIF.

• We created above method as static so that we need not to instantiate the class as static method can be directly called from class reference.

Thanks and Regards
Rahul Gupta